First, they were not previously thought to be common June breeders in coastal Sinaloa; thus, the dry and featherless ventral apteria observed in birds initiating breeding in July and August implied that they had bred earlier in the USA or Canada and not in Sinaloa.
2009) assumed that the featherless ventral apteria found in individuals of these species initiating breeding in July and August suggested they had bred earlier someplace to the north.
As we show below, the assumption that Yellow-billed Cuckoos initiating breeding in coastal Sinaloa in July and August with fully de-feathered ventral apteria fails to suggest earlier breeding in the same season because the ventral apterium of Yellow-billed Cuckoos is bare throughout the year.
We have taken care to assure that the nests and the conditions of ventral apteria reported here are all independent observations.
From 30 May-6 June 2011, we collected or netted and released five female chats that were incubating or about to lay: two with edematous or fully defeathered ventral apteria were presumably incubating, and three were females that were laying or about to lay, with their ventral apteria almost fully de-feathered (Table 1).
From 29 May-5 June, we collected or netted and released nine females with some down on their ventral apteria (Table 2).
All six of these birds had dry and fully de-feathered ventral apteria, yet four were moderately fat as though they were migrants.
UWBM specimens show that both sexes of Yellow-billed Cuckoos have defeathered ventral apteria when breeding.
Prior to the mid-winter molt, we expected that all adults might have de-feathered ventral apteria carried over from breeding in the previous season.
Second, the downy ventral apteria found in a number of female chats and orioles examined or collected in late May and early June of 2011 suggests that they were breeding for the first time in the summer in this region of coastal northwest Mexico.
We also visually inspected nestlings of lark sparrows for ectoparasites, including apteria
, feathers (if present), and facial, neck, and wing regions as described by Clayton and Walther (1997).